(1) Field of the Invention
This invention relates to the repair of motorized vehicles such as automotive gauges such as the oil pressure gauge, fuel gauge, and temperature gauge. An automobile repair mechanic is one having ordinary skill in this art.
(2) Description of the Problem and Related Art
Basically, all automobile gauges are shunted galvanometers which are calibrated for the appropriate reading. For example the measurements of oil pressure, temperature, or fuel level will be translated into an electrical output, and then the measurement of this electrical output will indicate on the dashboard of the automobile as to whether the fuel is full or half full, or whether the oil pressure is 15 pounds or 30 pounds.
One common form of galvanometers used as gauges on automobiles use, as a shunt, a ceramic plate with a resistance material on the back of the plate. The ceramic plate is rectangular and has a hole near each end of it. Bolts or studs extend from the back of the meter having two electrical connections to the meter. The holes in the plate telescope over these electrical connecting studs. Upon the back of the plate is painted the resistance material with an insulating cover also painted over the resistance material. The portion of resistance material surrounding the holes of the plate are not insulated so that an electrical connection is made at those two points.
It has been found that often the resistance material fails and the resistance separates, resulting in an open circuit. This causes a malfunction of the gauge. Normally, this occurs with the ceramic plate intact. The ceramic plate is a structural part of the meter as well as an electrical part of the electrical circuit of the meter.
In commercial practice, the ceramic plates are not available as a repair part. Therefore, when the resistance paint on the ceramic plate fails, the repair mechanic must replace the entire gauge.